1. Field of the Invention
The present invention relates to a polarizing member for use in forming an illuminator or a liquid-crystal display device which is hardly discolored at a wide viewing angle including a frontally viewing direction and an obliquely viewing direction.
2. Description of the Related Art
Various kinds of techniques have been heretofore known as techniques each using a reflective type polarizer to prevent discoloration in order to make luminance of a liquid-crystal display device high (Unexamined Japanese Patent Publication No. Hei. 4-268505, WO 95/17691, Unexamined Japanese Patent Publication No. Hei. 10-319235, and Unexamined Japanese Patent Publication No. Hei. 11-311710). On the other hand, there have been related-art proposals for preventing discoloration by addition of a light-diffusing layer (Unexamined Japanese Patent Publications No. 2001-154021 and 2001-166140). There is, however, a problem that luminance is lowered because of shortage of improvement in discoloration and elimination of polarization in an obliquely viewing direction.
Particularly in the technique of reducing the quantity of the change of chromaticity in hue between a frontally viewing direction and an obliquely viewing direction as suggested in Unexamined Japanese Patent Publication No. Hei. 10-319235, there is a problem that change of an elevation angle makes chromaticity be changed larger when the direction of discoloration varies in accordance with the elevation angle in oblique viewing. There is also a problem in rainbow-coloring such that a remarkable change of the view angle occurs in spite of a very small change of the elevation angle. On the contrary, when the quantity of the change of chromaticity between elevation angles is small in spite of a large quantity of the change of chromaticity in the frontal viewing direction, visibility is good. Hence, the necessity of performing evaluation by eye observation still remains in the technique. Accordingly, there is a disadvantage in that accurate evaluation cannot be achieved on the basis of comparison between hue at a frontal viewing angle and hue at an optional elevation angle by an apparatus.